The formation of stripes and the enhancement of pairing the anisotropic t-J model

We have examined the formation of stripes and pairing in the anisotropic t-J model using exact diagonalization methods on several different cluster sizes. We have found that as the values of the long-range hopping parameters increase, the holes are found to separate while enhancing the strength of the binding, resulting in a bi-directional stripe-like configuration of charge carriers. Evidence of unidirectional stripe formation in the hole and spin correlations is found upon consideration of the phase transition between the high-temperature tetragonal and low-temperature orthorhombic phases of La214, represented by an anisotropic next-nearest neighbor hopping parameter. Upon examination of the magnetic structure factor, the values closest to (*p, *p) are found to increase rapidly as a function of doping, indicative of the formation of incommensurate peaks. We have determined that the formation of stripes parallel to the Cu-O-Cu bonds enhances pairing and in the bulk limit there is a finite range of doping concentration where hole pairs will form. These results are consistent with the experimental data.